Servomotor shuttle guide assembly

ABSTRACT

A RECORDING INSTRUMENT HAS A SERVOMOTOR WITH A SHUTTLETYPE OF ARMATURE SUPPORTED ON BEARINGS SLIDABLE FREELY ON A PAIR OF GUIDE RODS PARALLEL TO A MAGNETIC POLE PIECE COAXIAL WITH THE ARMATURE COILS. THE POLE PIECE AND GUIDE RODS ARE SUPPORTED AT THEIR ENDS IN THE SIDE BARS OF A MAGNET FRAME. THE GUIDE RODS ARE PILACED IN TENSION BY NUTS AT OPPOSITE ENDS THEREOF, THREADEDLY RECEIVED THEREON AND HAVING SPHERICAL NOSES SEATED IN COUNTERSINKS IN THE SIDE BARS TO AVOID INDUCING ANY BOW IN THE GUIDE RODS.

221 Filed United States Patent [72] Inventor [21] AppLNo.

Ernest M. Hus Indianapolis, Ind. 799,035

Feb. 13, 1969 June 28, 1971 Esterllne Corporation New York, N.Y.

[45] Patented [73] Assignee [54] SERVOMOTOR SHUTTLE GUIDE ASSEMBLY 6 Chins, 4 Drawing Figs.

[52] US. Cl 335/209, 248/200, 346/32 [51] Int. H01t 7/00 [50] Field 01 Search 335/209,

[56] References Cited UNITED STATES PATENTS 1,352,918 9/1920 Rohbock 85/32 1,705,811 3/1929 Eidel v 85/32 3,184,754 5/1965 Peltola 346/32X 3,386,771 6/1968 Verdier 85/32X Primary Examiner-G. Harris Attorney-Woodward, Weikart, Emhardt and Naughton ABSTRACT: A recording instrument has a servomotor with a shuttle-type of armature supported on bearings slidable freely on a pair of guide rods parallel to a magnetic pole piece coaxia1 with the armature coils. The pole piece and guide rods are supported at their ends in the side bars of a magnet frame. The guide rods are placed in tension by nuts at opposite ends thereof, threadedly received thereon and having spherical noses seated in countersinks in the side bars to avoid inducing any bow in the guide rods.

Patented June 28, 1971 3,588,767

2 Sheets-Sheet 1 INVENTOR ERNEST M. HAAS ATTORNEYS Mom/1d,, Mafia/11,, @nlzamit WWW Pa tented June 28, 1911 3,588,767

2 Sheets-Sheet 2 INVENTQ ERNEST M. HAAS ATTORNEYS SERVOMOTOR SHUTTLE GUIDE ASSEMBLY BACKGROUND OF THE INVENTION 1 Field of the Invention I This invention relates generally to graphic recorders, and more particularly to a recorder having a shuttle-type of armature in the servomotor thereof, with particular attention directed to the mounting and guiding of the armature.

2. Description of the Prior Art Graphic recorders with shuttle-type armatures are known. A good example is described in the U.S. Pat. No. 2,58 l ,133 issued .lan. l, 1952 to Arthur W. Niemann. An improvement in the recorder described in that patent has been marketed by the assignee of the present application as the Esterline Angus Speed Servo" Model El 1018, for example. That instrument employed a guide rod and antitum rod for the armature, these rods being polished nonmagnetic rods slip-fitted in apertures in side bars of the servomotor magnet. Standard hexagonal nuts were threadedly received on the ends of these rods or shafts to locate and secure them in position in the side bars. Occasionally, if a condition of misalignment of the nut threads with the nut face existed, tightening of the nuts could induce a bow in the guide rod with adverse effects on performance of the armature shutting back and forth along the rods.

SUMMARY OF THE INVENTION Described briefly, in a typical embodiment of the present invention, the magnet frame side bars of a servomotor are provided with comparatively large apertures to allow free insertion of guide rods therethrough without scratching the guide rods. At the outer faces of the side bars, conical countersunk surfaces are provided concentric with the apertures. Hexagonal headed nuts are threadedly received on opposite ends of the guide rods, but are provided with spherical noses in contact with the countersink surfaces. The nuts are also provided with counterbores extending outwardly axially from the spherical noses to accommodate significant longitudinal variation in position of the nuts or extent of the threads thereon with respect to the shaft. This combination pennits the nuts to be self-centering as they are tightened to place the rods in tension. Being self-centering, they do not induce a bow in the rod even though there might be some misalignment of the threads with respect to the rod axis.

BRIEF DESCRIPTION OF THE DRAWINGS The full nature of the invention will be understood from the accompanying drawings and the following description and claims.

FIG. 1 is a rear'elevational view of a portion of a graphic recorder, showing the general arrangement of the magnet, magnet frame, pole pieces, armature and guide rod.

FIG. 2 is a side elevation thereof, including the chart mount and drive motor and chart marking pen (not known in FIG. I), with a portion of the magnet frame broken away to show the typical location of the antiturn rod as well as the main support and guide rod.

FIG. 3 is an enlarged section through a typical prior art mounting of a guide rod.

FIG. 4 is an enlarged section taken at line 4-4 in FIG. I and viewed in the direction of the arrows, with a portion of the guide rod omitted to conserve space, and omitting the armature, and illustrating the guide assembly according to a typical embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail, a magnet frame 11 is provided with a pair of side bars 12 and 13, a soft steel magnetic return path 14, and supports and permanent magnet 16 therein. A pole piece 17 of circular cross SECTION section is mounted to the side bars 12 and 13 and the armature shuttle 18 encircles the pole piece 17, the coil 19 thereon being adjacent the pole piece 21 is lS also supported by the magnet frame. The side flanges 22 and 23 of the shuttle have bearings in apertures therein received on the guide rod 24 which can be a solid or tubularshaft, the solid construction of nonmagnetic material being preferred. Similarly, the flange 23 has a notch 26 thereon received on the antitum rod 27 of construction like that of rod 24. The armature is thereby guided as it shuttles back and forth between bars 12 and 13 in response to electrical signals. I

According to the prior art construction shown in FIG. 3, the rod 24A, for example, would be mounted in aside bar 12A by reception through an aperture in the side bar. The aperture is of stepped diameter providing a portion 28 sized to provide a slip fit of the polished guide rod therein, and a portion 29 of larger diameter to provide ample clearance from the slip fit portion to the outer face 31 of the side bar. A hexagonal nut 32 was threadedly received on the rod 24A with the nut face 33 hearing on the side bar face 31. Slight out-of-square conditions between the thread axis of the nut or the guide rod with the face of the nut or side bar could induce a bow in the guide rod.

Referring now to FIG. 4, the side bars 12 and 13 are provided with apertures therethrough, and since both are alike, a description of one will suffice. The aperture 36 in the side bar 12 is of comparatively large diameter, allowing the guide rod to be assembled through the aperture without any chance of scratching the guide rod. The nut 37 having a hexagonal tool receiving surface thereon at 38, similar to that of the nut 32, has a spherical nose 39 and a counterbore extending from the aperture 41 at the inner end of the nose out to the point 42 where the threads begin and extend out to the outer face 43 of the nut. This spherical nose bears on the conical countersink surface 44in the side bar, located outboard of the aperture 36. The out is threadedly received on the guide rod 24 but, because of the bearing of the spherical surface on the conical surface, the nut is self-centering and, in effect, pivotally seated, so that any thread misalignment conditions are overcome and no bow is induced in the rod upon tightening. The axis of the thread on the rod can be out of parallel with the axis ofthe rod without a bow being induced in the rod.

By providing the construction according to the present invention, the guide rods can be placed under tension by tightening the nuts allowing the use ofa small sized (diameter) rod without concern about bowing due to tightening, because the present invention avoids it. The advantages of the present invention can be secured regardless of whether solid or hollow shafts might be used as guide members for the shuttle. It is also an advantage that because of the self centering feature, the guide rod need not contact the side bars at apertures 36 at any time, and it is preferable that it does not. The support for the rod is exclusively through the nuts 37 at the opposite ends thereof. It also should be recognized that some degree of selfcentering and pivotal seating can be obtained even if the nose of the nut is not a sphere ofsingle radius, and even if the seat is not strictly conical, as the seat might be concave and of greater radii than that of the nose of the nut. The present invention is applicable to guide rods in environments other than that specifically disclosed herein.

lclaim:

1. In a recording instrument, the combination comprising:

a magnet frame having spaced walls with countersunk apertures;

an armature shuttle linearly movable between said wall;

a guide member extending through said countersunk apertures in said walls and receiving said shuttle thereon; and

a retainer on each end of said guide member, said retainer being seated in said apertures precluding contact between said walls and said member.

2. The combination of claim 1 wherein:

said guide member is a first shaft with each end portion threaded;

said retainers are nuts threadedly received on said shaft,

each retainer having a convex surface bearing on a tapered surface of the wall in which it is seated.

3 4 I 3. The combination of claim 2 wherein said tapered surface 6. The combination of claim 5 and further comprising: is a conical surface. an additional guide shaft parallel to said first guide shaft and 4. The combination of claim 3 wherein said apertures being guidingly receiving said shu tl a additional ft inboard of id ie l surfaces d communicating being received in aligned apertures in said frame walls by h i h, 5 nuts at opposite ends thereof having spherical surfaces 5. The combination of claim 4 wherein said fasteners are received f bearing on foumersunk Surfaces in said tightened on said shaft and against said seat to place said shaft walls at apertures therem' in tension. 

